Darton Sleeves

FYI....

A customer brought in a LS-7 block for us to sleeve due to a bad cylinder with only 300 miles on it, unfortunately this was caused by a little NOS.

We finished pulling the sleeves out of a LS-7 block this week and noticed a few things...

The only difference between the LS-2 block and the LS-7 block is:

The LS-7 block comes with billet steel main caps with dowels but they use the same main bolts as the LS-2.

The "Displacement on Demand" holes are not drilled on the LS-7

The LS-7 was resleeved with a weak cast iron sleeve at a 4.125 bore.

The LS-7 block is stamped as a 7.0L.

Other than what is listed above the block seems to be identical to the LS-2 block but it has been resleeved. I will post pictures soon.....

niphilli

Great info...Keep us posted. I am guessing this means that the C5r Block is still the preferred block for high HP applicaitons.

Nine Ball

iTrader: (38)

Is the LS7 factory resleeved, or are the original sleeves cast in place like the LS1?

So, you can sleeve your LS2, and buy GM's billet mains and have an LS7 bottom end for all intended purposes.

NOSjohn

iTrader: (9)

Very interesting indeed!

Steve - Race Eng

iTrader: (1)

I worked on the LS7 block for Darton.

The LS7 block has pressed in gray cast iron sleeves. They are quite brittle. The bottom overhanging piston skirt support section broke on every sleeve during the removal process.

I have some photos attached of the block sans sleeves. The aluminum bores were found to be very badly machined. There is a barber pole finish in just about every bore.

I have heard from sources that the original LS7 blocks had cast in liners similar to the other production LS blocks. Apparently these failed. GM went to the pressed in liner. I have no clue if this block had cast in liners which were machined out for pressed in liners or if the block was cast without liners specifically for the pressed in liners. The barber pole finish is not the same as the outside finish of the cast in liners. This is clearly a machining defect.

A few of the aluminum bores had a half thou of taper and out of round. Some of the others were out almost four thou. This precludes having a direct replacement sleeve.

Darton will come out with a replacement ductile iron sleeve for this block. I want to have it large enough on the outside so the bores can be machined round with a nice finish. The Darton material will allow overbores to 4.150" and possibly larger if I have my way!

Steve

Wet 1

iTrader: (4)

Great info guys, thank you!!!

Steve, you guys are mad-men boring these blocks out to 4.150"+, there must be nothing left between the bores at this point!

Thanks again guys...

98Z28CobraKiller

iTrader: (17)

How could that bore have passed any kind of QC? You would have to be blind not to see the "barber pole bore".

Camaro_Zach

iTrader: (19)

thats cause they got this guy doin the machine work on the ls7's

Darton Sleeves

Or you can go with our dry sleeve 4.125 kit with our "Seal Tight Technology" for the LS-2 for $1600.00 installed and add any main caps you want.

JBT

So aroud $2600 for a new ls2 block with 4,125 bore!?

Steve - Race Eng

iTrader: (1)

It runs right around $2,700 to do the LS2 dry sleeve with me supplying a new stress relieved core. The cores must be stress relieved for the cylinders to stay round after use. This is true even if the block is not sleeved!

If you want a complete engine or short block using one of my Darton LS2 dry sleeved blocks, contact: Mikey at Rapid Motorsports, Erik at Horsepower Engineering, or Alan Futral.

Steve

mikey

iTrader: (6)

We have two of Steve's LS2's going together now at 4.125". One is a 427 and the other is a 441. Having seen the LS7 block in person, I much prefer the re-sleeved LS2 blocks.

SuperSporttruck

iTrader: (2)

Great info guys, I would have figured that GM would have made a different block for the Z06, but i guess you guys have found out the blocks are crap. I have a feeling its gonna bite GM in the butt with guys blowing these up under warrenty.

Bill Reid

iTrader: (14)

A sleeve manu and a guy who stuffs them posting crap about the LS7 block looks like a profit making propoganda business decision to me... well before it looks like a consumer alert. Any machinest can post crappy pics of a block after the sleeves are pulled and pitch the significance of what the block looks like afterwards. Bottom line is the block was smoked because the owner and/or tuner of it is an idiot... not because of the blocks strength, the way GM engineers desgined it, or how factory machinests prepped the block for sleeves.

When the LS7 block becomes available there will be guys that buy it and push power levels beyond its engineered limits. I won't hold my breath on the significance of "barber poling" and how it can affect the strength of the block and/or the "gray" sleeve.

What I would like to see is LS2 and LS7 blocks/pieces disected and next to each other proving the accusation that they are one in the same casting...

CrabhartLS1

Interesting bit of info. Kind of like the LS1/LS6 block differences.

52172

iTrader: (2)

Except a little more interesting indeed. Anyone who has purchased an ls7 is going to have a hard time facing reality!

Slowhawk

iTrader: (12)

That really sucks because I was under the impression these 7.0 blocks would be good to build on.Now, by the looks of it,they are just crap.I was not expecting the blocks to use pressed in liners.We were hoping they would be close to a C5R design. So the liner's could be crap,the rods are weak and who knows what else.What a waste of $70g's.

2002_Z28_Six_Speed

iTrader: (19)

Just noting the amount of material between the cylinders. WOW. What is the structural intergerity of that block? I know it would be stronger than I am thinking with the sleeves installed, but man there is just no material there. How can that motor take any lateral shock?

Steve - Race Eng

iTrader: (1)

The GM press in sleeves are 4.300" outside diameter. That leaves .100" of aluminum between the sleeves.

What may lead to problems (faulure) is the liner itself being gray iron and not ductile iron. Gray iron rarely exceeds 50,000 psi tensile strength, is quite brittle and will crack under detonation.

The Darton sleeve for the LS2 dry is made of 110,000 psi minimum tensile strength ductile iron. You can hit the sleeve with a hammer and it will bend but will not crack. If you try that with a gray iron sleeve you better be wearing eye protection because it will shatter.

I got after Darton to make a large bore dry sleeve for the LS2 blocks. I specified the body and flange diameters during the design process. The Darton LS2 dry sleeve has an upper body (piston thrust area) outside diameter of 4.325". Since the sleeve is so much stronger than the stock gray iron liner, the block can be thinner between the cylinders and not pose a problem. In fact the top fuel sleeves are made of the exact same material and are only slightly thicker than the Darton LS2 dry sleeves.

There is no real problem with properly designed and installed dry liners contrary to what some think. It is less expensive for the factories to cast in the liners which is why most production blocks are made that way. The block is also somewhat lighter with the cast in liner. I know that Ford uses pressed in liners in the Mod blocks as does Dodge in the Viper blocks.


Steve

52172

iTrader: (2)

are the darton 4.20 MID sleeves available yet? steve?